Objectives: Effects of group size, population density and competition between strains on agonistic behavior, social mobility and female reproductive fitness are to be evaluated. Method: Preliminary results indicate that a reversal of social dominance ability occurs between two strains of chickens between adolescence and full maturity. Initial pair contests will be conducted at several ages to establish this event with greater precision. Agonistic behavior and components of female reproductive fitness will be measured in flocks differing in group size, population density and genetic composition. Particular emphasis will be placed on relative social dominance potential of the two strains, as indicated by pair contest results, and their social status in intermingled strain flocks to determine the importance of social inertia in different social environments.